This invention relates to an anchor and/or guide balloon, stent catheter in the field of coronary and peripheral angioplasty. More specifically, this invention relates to accurate stent placement and balloon deployment at a stenotic site within a patient's vascular system, usually at a bifurcation site, while maintaining lumen access for insertion of marker fluid and blood flow during an angioplasty stenting procedure.
The vascular bed in humans is a complex and extensive network of lumens carrying blood and delivering oxygen and nutrients throughout the skeletal network, organs and muscle tissues of the body. At a macro level the human circulatory system can be logically characterized as originating from the heart with a briefly ascending aorta from the left ventricle upwardly into an arch and then descending generally vertically downward via a central lumen column through a patient's thoracic region and diaphragm to an abdominal aorta segment. The aorta terminates with common left and right iliac arteries extending into femoral arteries and down into popliteal arteries and distally to extremities of a patient's legs.
In general terms the aorta provides a base for systemic circulation for the entire body. Right and left coronary branches extend from an aortic root to supply a patient's heart while an aortic arch supplies blood to the patient's head, neck and arms. Branches from the thoracic aorta supply the chest and branches from the abdominal aorta supply the abdomen and kidneys while the pelvis and lower extremities are fed from common iliac arteries extending from a base region of the aorta.
The human vascular system, originating from the heart, is composed of a series of flexible lumens decreasing in diameter and increasing in branches. In broad terms a sequence of blood flow is from a left heart ventricle to an aorta, to arteries, to arterioles, to venules, to veins, and to a vena cava back to a right side of the heart.
Vascular lumens are composed of elastic tissue which can, over time, become somewhat hardened in a disease zone due to an internal accumulation of cholesterol laden plaque, which is a fatty material composed of cholesterol and other particles which build up within an artery wall to create a narrowing (stenosis) of the artery. Plaque stenotic segments can decrease vessel elasticity and concomitantly occlude a free flow of blood through the lumen. This malady is sometimes referred to as atherosclerotic arterial disease. Stenotic segments usually occur at lumen junction sites but can form at other locations throughout a human vascular system.
In 1964 an vascular radiologist by the name of Charles Dotter, often referred to as the “Father of Interventional Radiology” pioneered development of angioplasty and a catheter delivered stent as a treatment for peripheral arterial disease.
Stents are now universally used in percutaneous coronary and peripheral angioplasty procedures, which effectively open narrowed blood vessels. A stent is a tiny, expandable, cylindrical wire mesh scaffolding, which may be mounted on a deflated balloon in a “crimped” or collapsed state. A cylindrical stent scaffolding is inserted into a narrowed stenotic segment of an artery over a thin angioplasty guide wire via a catheter sheath and then expanded by inflating an internal, coaxial, cylindrical stent balloon.
A thin angioplasty guide wire is advanced, through the guide catheter, into a blood vessel and inserted through a narrowed lumen stenosis. A stent (with an interior, concentric, collapsed, tubular balloon) is introduced, over the angioplasty guide wire, through the guide catheter and accurately positioned at the lumen stenosis site. High pressure (nine to eighteen atmospheres) is then used to radially inflate the cylindrical balloon and permanently expand the wire stent scaffolding outwardly to radially expand and compress plaque at the lumen stenosis segment, resulting in a central enlarged opening inside the lumen for improved blood flow. The internal cylindrical balloon that is used to operably expand the stent is thereafter deflated and withdrawn along with the guide wire and catheter guide sheath while the expanded wire stent scaffolding remains positioned at the stenotic site.
An interventional physician uses radiography, an X-ray procedure, to identify a stenosis location and estimates the size of a diseased blood lumen and severity of stenotic plaque narrowing. Blood vessels are not visible by X-ray, per se, however, by injecting a contrast media (dye) through the catheter sheath a trained physician is capable of accurately viewing arterial boundaries carrying a pulsating flow of blood through the lumen and can develop an accurate sense of a stenotic site requiring interventional correction.
Placing a stent at a site of a stenosis in a downstream segment of a blood vessel is now considered a routine process. When plaque stenosis narrowing is located at a bifurcation opening of the blood vessel from the aorta, or at a downstream bifurcation site where a blood vessel branches, however, optimal placement of the stent is more challenging. In this, positioning a stent too distal may miss part of a narrowing stenosis while positioning a stent too proximal may result in proximal end of the stent protruding into a primary blood vessel.
Examples of challenging locations are plaque stenosis occurring at an opening of arteries originating from the aorta: the left main coronary artery, the right coronary artery, the innominate artery, left common carotid artery, left subclavian artery, celiac artery, superior mesenteric artery, inferior mesenteric artery, the left and right renal arteries and iliac arteries. Other examples include vessel bifurcations downstream in the coronary arterial tree such as the left anterior descending and the left circumflex coronary arteries which bifurcate from the left main coronary artery. It also includes peripheral arteries such as the common femoral arteries bifurcations.
Due to the complexity of accurately positioning a stent at a vessel bifurcation opening, in a pulsating circulatory system, stenting a stenosis at a bifurcation requires a longer operative time, exposing a patient and staff to extra radiation during the angiography, and injecting larger amounts of radiopaque contrast media which may compromise the patient's hemodynamic status and kidney functions. It is not uncommon for an interventional physician to use additional stents because of non-satisfactory initial results due to stent malposition. The procedure may therefore become prolonged and complex, carrying out higher risks and a higher rate of complications.
In order to address this problem it has been previously suggested to use a two part balloon stent catheter, where a relatively large torus part of a balloon is positioned at a proximal end of a cylindrical stent balloon. The inflated torus balloon serves as a stop at a bifurcation junction to prevent the stent on the cylindrical companion stent balloon from extending too far into a bifurcated lumen. At least one limitation of such a torus stop balloon, however, is that it will also temporarily limit or even occlude blood flow into a target vessel during stent positioning. It may also block a desired flow of contrast media (dye) from reaching a target vessel. In this, contrast media is often used to confirm the final positioning of the stent before radial deployment.
To address and ameliorate negative issues associated with a stop torus and concomitantly address a desire for a more sophisticated and accurate stent placement at stenotic bifurcation sites the subject invention is directed to a low pressure (one or two atmospheres) arcuate anchor and/or marker balloon segment or segments located at the proximal end of the stent balloon. The arcuate anchor and/or marker balloon segment (or segments) is separate from the cylindrical stent expansion balloon and will enable a free flow of blood and contrast media during a stenting procedure. In addition an arcuate anchor and/or marker balloon will provide a specific identification of a main vessel site to accurately position a conventional stent at the opening of the bifurcating vessel without protruding into the main vessel, using both angiography and tactile feedback, while reducing the use of contrast media.
Further although the subject anchor and/or marker system has primary function at a junction stenotic site frequently a straight vessel has small side branches, immediately before or after a stenosis. Inflating an anchor and/or marker balloon at a side branch, whether proximal or distal to the stenosis, can be used to localize the side branch cover it and protect it from getting covered when positioning a stent. This will also stabilize the stent prior to expansion in a pulsating arterial flow where the stent may be rocking back and forth during positioning due to pulsation blood flow. In this, if a stent is allowed to undesirably cover a side branch (sometimes referred to as jailing) blood flow to the side branch can be compromised.
The anchor and/or marker balloon segment (or segments) mounted on generally at a proximal or distal end of a stent is percutaneously inflated via a small independent tube or tubes within the deployment catheter using contrast media. By the provision of angiography and tactile feedback, a visible inflated marker and/or anchor and balloon at a proximal of the stent balloon is gently advanced and retracted to optimally face a stenotic site to be enlarged. Final balloon stent positioning may be confirmed by injection of contrast media via the guide catheter past the marker and/or anchor balloon segment or segments, before the stent balloon is inflated by application of internal high pressure.
Inflation pressure for the arcuate marker and/or anchor balloon segment or segments at a proximal or distal end of the stent is substantially less than the operating pressure of a conventional internal stent balloon. While a stent balloon needs a special inflation device to reach pressures between nine and eighteen atmospheres, the subject arcuate marker and/or anchor balloon segment or segments can be advantageously inflated to only one or two atmospheres by a hand syringe. Moreover, a blood lumen wall may, in some situations, have a curved or asymmetric geometry. A low pressure marker and/or anchor and guide balloon arcuate segment or segments can advantageously be used to facilely enhance alignment within a blood lumen wall by controlling the amount of pressure applied to a particular balloon segment or set of balloon segments in the marker and/or anchor and guide balloon(s).
The anchor and/or marker balloon segment or collectively segments do not extend a full three hundred and sixty degrees circumferentially around the deployment catheter. The arcuate shape of the subject low pressure marker and/or anchor and guide balloon segment or segments will accommodate and accurately identify a main vessel wall location, at a bifurcation of a blood vessel stenotic site. The arcuate shaped marker and/or anchor balloon segment or segments, in contrast to a full circumferential configuration, will advantageously not occlude blood flow to a target vessel and will concomitantly allow passage of contrast media during stent positioning.
The limitations suggested in the preceding are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness, reliability and physician/patient satisfaction with prior methods and apparatus for angioplasty, with stenting, at stenotic sites within a patient's circulatory system. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that present angioplasty method and apparatus, involving stenting a stenotic lumen in a patient's vascular bed, appearing in the past will admit to worthwhile improvement.